Wireless communication system and wireless communication control method, wireless communication device and wireless communication method, and computer program

ABSTRACT

A wireless communication device in a wireless network sets management information notification cycles at specified time intervals and transmits management information containing receive timing information showing its own position to start receiving information, receive window information, and receive cycle information. Another wireless communication device receiving that management information links it to a communication device number for the corresponding wireless communication device and stores the receive timing, the receive window information, and the receive cycle information. When sending information, the receive start position of the corresponding communication device is found from the receive timing information, the receive window information, and the receive cycle information of the other communication and information is then transmitted at that timing. An asynchronous ad-hoc communication wireless network can therefore be configured without a particular control station.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/452,013, filed on Apr. 20, 2012, which is a continuation of U.S.application Ser. No. 12/487,015, filed on Jun. 18, 2009, now U.S. Pat.No. 8,199,682, which is a continuation of U.S. application Ser. No.10/469,281, filed on Feb. 2, 2004, now U.S. Pat. No. 7,561,539, which isa national stage application under 35 U.S.C. §371 of InternationalApplication No. PCT/JP03/00832, filed Jan. 29, 2003, which claimspriority from Japanese Application No. P2002-28128, filed Feb. 5, 2002,the disclosures of which are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a wireless communication system andwireless communication control method, a wireless communication deviceand wireless communication method, and a computer program forcommunicating between multiple wireless stations as in a wireless LAN(Local Area Network). More particularly, the present invention relatesto a wireless communication system and wireless communication controlmethod, a wireless communication device and wireless communicationmethod, and a computer program for configuring a wireless network byad-hoc communication without installing a particular device serving asthe control station.

More precisely, the present invention relates to a wirelesscommunication device and wireless communication method, a wirelesscommunication device and wireless communication method, and a computerprogram for configuring a wireless network wherein terminals communicatedirectly (random access) and asynchronously with each other withoutinstalling a particular device service as the control station, and stillwore particularly relates to a wireless communication system andwireless communication control method, a wireless communication deviceand wireless communication method, and a computer program forconfiguring a wireless network wherein terminals communicate directly(random access) and asynchronously with each other while checking thepresence of other terminals.

2. Background Art

Along with increasingly sophisticated computer functions, local areanetworks (LAN) configured by connecting multiple computers have become apopular method for sharing information such as electronic files and dataor peripheral equipment such as printers and for exchanging informationby e-mail and data transmission.

In the related art, local area networks (LAN) use optical fibers andcoaxial cables or twisted-pair cables and each computer is connected viawire or cable. These wired LAN require installing cables and wiring aswell as complicated cable layouts that make it difficult to configure aLAN system. Furthermore, once a LAN system has been configured,equipment and components can only be moved within an area limited by thecable length, making these wired LAN inflexible and inconvenient.

Wireless LAN have become the focus of much attention as network systemsthat free users from the restrictions of LAN wiring in the related art.These wireless LAN eliminate most of the cable wiring used in workspaces such as in offices and make it relatively easy to movecommunication terminals such as personal computers (PC).

In recent years, wireless LAN systems have come into increasing demandas their speed becomes faster and cost becomes less expansive. Veryrecently in particular, personal area networks (PAN) made up orsmall-scale wireless networks for exchanging information among themultiple pieces of electronic equipment used around people in daily lifeare under evaluation. The industrial standards IEEE802.11b andIEEE802.11a, for example, are widely known as standards for wirelessLAN.

In methods for creating local area networks using wireless technology,one device called the “access point” is installed as a control sectionin the area, and the network is formed under the overall control of thiscontrol station.

In wireless networks installed with this access point, an access controlmethod based on bandwidth reservation is widely employed to transmitinformation from a communication device. In this method, the bandwidthrequired to transmit information is reserved at the access point so asto utilize the transmission line without causing conflicts withinformation transmission by other communication devices. In other words,synchronous wireless communication is performed by installing an accesspoint that permits communication devices in a wireless network tocommunicate in synchronization with each other.

Another method for configuring a wireless network called “ad-hoccommunication” was proposed that allows direct asynchronouscommunication between terminals. In a small-scale wireless networkcomposed of a relatively small number of clients located near eachother, this ad-hoc communication is ideal because all terminals in thenetwork can directly communicate with each other asynchronously withoututilizing a particular access point.

In a communication system composed of multiple terminals, access controlis essential for preventing communication between terminals fromconflicting with each otter. Several methods are available forperforming access control in a wireless network. These methods can bedivided into two groups. One group is channel occupancy methods forexample, FDMA (Frequency Division Multiple Access), TDMA (Time DivisionMultiple Access) and CDMA (Code Division Multiple Access). The othergroup is channel sharing methods such as ALOHA and CSMA (Carrier SenseMultiple Access). A method called CSMA/CA (Carrier Sense Multiple Accesswith Collision Avoidance) is commonly used for access control whenperforming asynchronous communication in small-scale wireless networks.

In as access control method called CSMA/CD (Carrier Sense MultipleAccess with Collision Detection), whether or not conflicts are occurringwith information transmissions from other communication devices isdetected by receiving a self-issued information signal. This method ismainly used in communication using cable and wires. In wirelesscommunication, on the other hand, it is difficult to receive aself-issued information signal. To avoid conflicts in wirelesscommunication, the CDMA/CA method starts transmitting information afterchecking that there are no information transmissions from othercommunication devices. This type of access control allows multipleterminals on the same wireless transmission line to share access andcommunicate with each other (multiple access).

Another example in the related art of transmission methods forcommunicating by random access is a method wherein all communicationdevices connected to one network constantly monitor information beingsent through the transmission line and the communication devicerequested to send information then sends it through the transmissionline.

Another further example in the related art of transmission methods forasynchronous communication of the related art is a method therein eachcommunication device decodes all received signals and only detectsinformation sent addressed to that communication device.

However, wireless communication still has the problem that conflictsoccur when multiple communication devices start transmitting informationsimultaneously. To solve this, a corrective method called RTS/CTS wasproposed that transmits information after a connection has beenestablished by sending as RTS (Request to Send) to the receivingdestination communication device before transmitting information andalso by receiving a CTS (Clear to Send) returned from the informationreceiving destination.

An stated above, an access point is required for controlling access toperform synchronized wireless communication within a wireless network.

In a wireless communication system having this access point, wirelesscommunication must be performed via this access point duringasynchronous communication between the transmitting and receivingcommunication devices. This creates the problem that transmission lineutilization efficiency is reduced by half.

Furthermore, when using a system that reserves a portion of thetransmission line, the transmission bandwidth must be reserved after thedemand has arisen for asynchronous transmission. In a wirelesscommunication system using time division multiplex access (TDMA), thisalso creates the problem that information cannot be quickly transmitted.

In such wireless communication systems using time division multiplexaccess, the terminals must be synchronized with each other even duringdirect transmission between terminals without via the access point,making it difficult to achieve control.

On the other hand, during asynchronous communication in an ad-hocwireless network in which terminals can communicate directly withoututilizing an access point, the transmitting communication device mustcheck in advance for the receiving communication device.

Furthermore, when transmitting information asynchronously, a redundantpreamble signal must also be added to the information so that thereceiving communication device can detect that the informationtransmission has already started.

For example, in UBW (Ultra Wide Band) wireless communication thatperforms high speed data transmission by diffusing the transmission datainto an extremely low frequency bandwidth, there is no carrier such asused for wireless communication in the related art. A preamble signalwith even higher redundancy must therefore be added to the beginning ofthe information transmission so that the receiving terminal caninitially synchronize with the information signal by detecting whetherthe signal is present or not.

When performing access control based on the CSMA/CA (Carrier SenseMultiple Access with Collision Avoidance) method, the problem occursthat conflicts cannot be detected if multiple communication devicesstart transmitting information simultaneously.

Asynchronous communication methods or the related art have the fatalflaw that receiving must be performed all the time to captureinformation that is sent at an unknown time from a communication devicein the network. Wireless communication devices must therefore constantlykeep receiving in order to perform asynchronous information transmissionby wireless communication, making it impossible to reduce powerconsumption.

In asynchronous receive methods that must decode all the receivedsignals in order to detect in rotation addressed to itself, a large loadis imposed on the receive processing. This requires a high speedprocessor and/or special devices and therefore increases the cost.

In asynchronous receive methods that must decode all the receivedsignals in order to detect information addressed to itself, a large loadis imposed on the receive processing. This requires a high speedprocessor and/or special devices and therefore increases the cost.

When applying the RTS/CTS access control method to asynchronous wirelesscommunication, each terminal must constantly keep receiving in order todetect the short RTS signal. This constant receiving of course makes itdifficult to reduce power consumption. Even though standards exist forthe RTS/CTS access control method, it is recognized as less effectivefor use with communication devices.

It is desirable to provide an excellent wireless communication systemand wireless communication control method, a wireless communicationdevice and wireless communication method, and a computer program,wherein terminals can directly communicate with each other withoutinstalling a particular device serving as the control station.

It is further desirable to provide an excellent wireless communicationsystem and wireless communication control method, a wirelesscommunication device and wireless communication method, and a computerprogram, capable of forming a wireless network with terminalscommunicating directly and asynchronously with each other.

It is still further desirable to provide an excellent wirelesscommunication system and wireless communication control method, awireless communication device and wireless communication method, and acomputer program, capable of forming a wireless network in whichterminals communicate asynchronously with each other while checking forthe presence of other terminals.

It is also desirable to provide an excellent wireless communicationsystem and wireless communication control method, a wirelesscommunication device and wireless communication method, and a computerprogram, capable of forming a wireless network in which terminalscommunicate asynchronously with each other while sending signalscontaining beacon information to other terminals.

It is yet further desirable to provide an excellent wirelesscommunication system and wireless communication control method, awireless communication device and wireless communication method, and acomputer program, wherein communication devices transmit informationasynchronously without being in constant receive standby.

Even further desirable is to provide an excellent wireless communicationsystem and wireless communication control method, a wirelesscommunication device and wireless communication method, and a computerprogram, whereby communication devices can perform asynchronous wirelesscommunication by RTS/CTS control without being in constant receivestandby.

BRIEF SUMMARY OF THE INVENTION

A first aspect of the present invention is a wireless communicationsystem or wireless communication control method for asynchronousinformation transmission between multiple communication devices, whereinmanagement information containing the receive processing timing of one'sown communication device is exchanged between the wireless communicationdevices; and the transmitting source wireless communication device sendsinformation to the receiving destination wireless communication device,by utilizing the receive processing timing described in the managementinformation.

The term “system” as referred to here, is logical aggregate of multipledevices (or functional module for implementing a designated function)and makes no special reference to whether or not the devices orfunctional modules are in a single enclosure.

Here, the management information contains timing information for settingthe receive window and contains cycle information for setting thereceive window so the wireless communication device can perform receiveprocessing. The management information may also contain device IDinformation unique to each corresponding wireless communication device.

Each wireless communication device links the device ID information uponreceiving the management information from other wireless communicationdevices and in this way multiple wireless communication devices cancontrol the receive processing timing.

Therefore, according to the wireless communication system or wirelesscommunication control method in the first aspect of the presentinvention, a wireless network can be formed, wherein each wirelesscommunication device checks the presence of the other communicationdevices by exchanging management information, and performs asynchronouscommunication based on receive timing described in the managementinformation. In this case, each wireless communication device cancommunicate directly and asynchronously without installing a particulardevice serving as the control station.

Furthermore, according to the wireless communication system or wirelesscommunication control method in the first aspect of the presentinvention, each wireless communication device notifies in advance theother communication devices of its own receive timing, receive windowand receive cycle information, and transmits information by utilizingthat receive window. In other words, each wireless communication devicecan communicate asynchronously without being in constant receivestandby, thus allowing the receiving function to operate with low powerconsumption.

Furthermore, according to a wireless communication system or wirelesscommunication control method in the first aspect of the presentinvention, wireless communication devices can perform wirelesscommunication without having to obtain a means to check in advance ontransmission line usage, by transmitting information based on themanagement information received in the past, so that informationtransmission is performed in a comparatively short time.

In other words, according to the wireless communication system orwireless communication control method in the first aspect of the presentinvention, an access control method capable of avoiding conflicts duringasynchronous wireless communication can be obtained without using arandom access control method for avoiding communication conflicts bycarrier sensing control.

In the wireless communication system or wireless communication controlmethod in the first aspect of the present invention, each wirelesscommunication device arranges the receive window by shifting the timingso that receive processing periods do not overlap with periods of othercommunication devices, thus achieving an access control not prone toconflicts between multiple wireless communication devices.

Also, each wireless communication device may transmit its own managementinformation at each specific cycle, and the management information maycontain notification cycle information for transmitting the managementinformation to other wireless communication devices.

Furthermore, each wireless communication device may check in response toreceiving the management information whether the corresponding wirelesscommunication device is present in the wireless network, and may alsodecide that the wireless communication device is no longer present inthe wireless network when a specified time (for example, a notificationcycle specified in the management information) has elapsed after lastreceiving the management information.

Specifically, a wireless network system for configuring an autonomouswireless network can be achieved within the communication range of awireless communication device without having to strictly define thewireless network, by providing a function to decide there is no longer aconnection with a wireless communication device and delete it from thememory when no signals containing the identifier and timing informationare received from that wireless communication device over a certainlength of time.

An access control method effective for use with multiple communicationdevices can also be achieved in synchronization with each other withouthaving to install the control station or access point serving as areference in the wireless network, by installing a managementinformation exchange area to exchange management information betweenmultiple communication devices.

Furthermore, in situations when transmission with a guaranteed qualityof service (QoS) is required, wireless communication with a guaranteedQoS can be easily achieved by communicating management information tonotify that transmission will be made with a guaranteed QoS as, forexample, in reserved transmissions.

Furthermore, by sending the management information of a communicationdevice to notify of the presence or absence of the other communicationdevices capable of communicating with that communication device, thestructural area for a wireless network centering on that communicationdevice can clearly be shown.

The transmitting source wireless communication device, along withsending an RTS (Request to Send) by utilizing the receive windowdescribed in the management information of the receiving destinationwireless communication, may start sending information by setting aconnection in response to receiving a CTS (Clear to Send) from thecorresponding receiving destination wireless communication device.

Therefore, according to the wireless communication system or wirelesscommunication control method in the first aspect or the presentinvention, communication devices can perform asynchronous wireless byRTS/CTS access control, without having to be in constant receive standbyfor detecting RTS signals.

Each wireless communication device also performs the minimum requiredreceive operation by respectively setting a minimum required receivewindow while mutually exchanging the management information. Unlike therelated art, there is therefore no need to be in constant receivestandby, so operation with low power consumption is achieved. Since thereceive window need only detect if there is information addressed to itsown communication device, an extremely short receive window can be setso that operation with exceptionally low power consumption is achieved.

Furthermore, the receive operation can be simplified by setting therespective receive windows as needed, since there is no need to receiveand decode all information flowing on the transmission lines even duringsuper high speed wireless transmissions.

Information addressed to one's own communication device can be acquiredwithout having to utilize a high-speed processor for receivinginformation sent in a super high speed transmission.

Here, in response to sending an RTS to the receiving destinationwireless communication device, the transmitting source wirelesscommunication device may receive a CTS from the receiving destinationwireless communication device by setting a confirmation receive windowfor receiving the CTS and then utilizing the confirmation receivewindow. Alternatively, the wireless communication device that receivedan RTS may return a CTS by utilizing the receive window described in themanagement information of the transmitting source wireless communicationdevice.

Furthermore, the receiving destination wireless communication device, inresponse to returning the CTS to the transmitting source wirelesscommunication device, may set an information receive window forreceiving information from the transmitting source wirelesscommunication device, and the transmitting source wireless communicationdevice may send information by utilizing the information receive window.Alternatively, the transmitting source wireless communication device, inresponse to receiving the CTS sent from the receiving destinationwireless communication device, may send information by utilizing thereceive window described in the management information of the receivingdestination wireless communication device.

Furthermore, after the information transmission is complete, a receiptconformation may be exchanged between the wireless communication deviceson the transmitting and receiving sides. In this case, the transmittingsource wireless communication device, after sending the information, mayset a receipt confirmation receive window for receiving a receiptconfirmation from the receiving destination wireless communicationdevice, and the receiving destination wireless communication device mayalso send a receipt confirmation by utilizing the receipt confirmationreceive window. Alternatively, the receiving destination wirelesscommunication device, after receiving the information sent from thetransmitting source wireless communication device, may send the receiptconfirmation by utilizing the receive window described in the managementinformation of the transmitting source wireless communication device.

A second aspect of the present invention provides a wirelesscommunication device for asynchronous information transmission over awireless network, comprising: a receiving means for receivinginformation, a management information storage means for linkingmanagement information received from other wireless communicationdevices to the corresponding wireless communication device and storingthe management information, a transmitting means for transmittinginformation; and an access control means for controlling the transmitand receive timing of the receiving means and transmitting means byutilizing the receive processing timing described in the managementinformation of the receiving destination wireless communication.

A third aspect of the present invention provides a wirelesscommunication method for asynchronous information transmission over awireless network, comprising the steps of: receiving the managementinformation describing the receive processing timing on thecorresponding wireless communication device, from other wirelesscommunication devices; storing the received management information whilelinking it to the corresponding wireless communication device; andsending information by utilizing the receive processing timing describedin the management information of the receiving destination wirelesscommunication device.

Here, the management information contains timing information for settinga receive window for the wireless communication device to performreceive processing and also contains cycle information for setting thereceive window. The management information may also contain device IDinformation unique to the corresponding wireless communication device.

According to the wireless communication device in the second aspect ofthe present invention or a wireless communication method in the thirdaspect of the present invention, the management information receivedfrom other wireless communication devices is linked to the device IDinformation and stored so that the timing for multiple wirelesscommunication devices to perform receive processing or in other words,the timing for sending information so each wireless communication devicecan be determined as desired.

According to the second and third aspects of the present invention,wireless communication devices can perform wireless communicationwithout obtaining a means to check in advance on transmission lineusages, by transmitting information based on the management informationreceived in the past, so that information transmission is performed in acomparatively short time.

Specifically, according to the second and third aspects of the presentinvention, an excellent access control method capable of avoidingcollision during asynchronous wireless communication can be implementedwithout using a random access control method for controlling collisionavoidance by carrier sensing.

Furthermore, each wireless communication device may transmit its ownmanagement information at each specific cycle, and managementinformation may also contain notification cycle information fortransmitting the management information to other wireless communicationdevices. In the wireless communication device in the second aspect ofthe present invention or the wireless communication method in the thirdaspect of the present invention, each wireless communication device maycheck in response to receiving the management information, whether thecorresponding wireless communication device is present in the wirelessnetwork, and may also decide that the wireless communication device isno longer present in the wireless network when a specified time (forexample, a notification cycle specified in the management Information)has elapsed after last receiving the management information.

Specifically, a wireless network system for configuring an autonomouswireless network can be achieved within the communication range of awireless communication device without having to strictly define thewireless network, by providing a function to decide there is no longer aconnection with a wireless communication device and delete it from thememory when no signals containing the identifier and timing informationare received from that wireless communication device over a certainlength of time.

Furthermore, wireless communication with a guaranteed QoS can be easilyimplemented for a wireless communication device that gives advancenotification that transmission of management information with aguaranteed QoS is required as, for example, in reserved transmissions,by referring to its management information at the time of transmittingthe information.

In the wireless communication device in the second aspect of the presentinvention or in the wireless communication method relating to the thirdaspect of the present invention, the transmitting source wirelesscommunication device, along with sending an RTS by utilizing the receivewindow described in the management information of the receivingdestination wireless communication, may start transmitting informationby setting a connection in response to receiving a CTS from thecorresponding receiving destination wireless communication device.

Therefore, the receiving destination wireless communication device canperform asynchronous wireless communication by RTS/CTS access controlwithout being in constant receive standby for detecting RTS signals.

Here, in response to sending an RTS to the receiving destinationwireless communication device, the transmitting source wirelesscommunication device may receive a CTS from the receiving destinationwireless communication device by setting a confirmation receive windowfor receiving the CTS and then utilizing the confirmation receivewindow.

Furthermore, the transmitting source wireless communication device maysend information by utilizing the information receive window establishedby the receiving destination wireless communication device afterreturning a CTS. Alternatively, in response to receiving the CTS sentfrom the receiving destination wireless communication device, thetransmitting source wireless communication device may send informationby utilizing the receive window described in the management informationof the corresponding receiving destination wireless communicationdevice.

Furthermore, after the information transmission is complete, a receiptconfirmation may be exchanged between the wireless communication deviceson the transmitting and receiving sides. In this case, after sending theinformation, the transmitting source wireless communication device maysend a receipt confirmation by setting a receipt confirmation receivewindow for receiving a receipt confirmation from the receivingdestination wireless communication device.

Furthermore, a fourth aspect of the present invention is a wirelesscommunication device for asynchronous information transmission over awireless network, comprising: a management information creation meansfor creating management information describing the receive processingtiming of one's own device; a receiving means for receiving information;a transmitting means for transmitting the management information; and anaccess control means for controlling the receive timing of the receivingmeans based on the management information, and also controlling thetransmit timing of the transmitting means to transmit the managementinformation.

Furthermore, a fifth aspect of the present invention is a wirelesscommunication device for asynchronous information transmission over awireless network and comprising the steps of: creating managementinformation describing the receive processing timing of one's owndevice; sending the management information to other wirelesscommunication devices; and receiving information by utilizing thereceive processing timing described in the management information.

Here, the management information contains timing information for settinga receive window for the wireless communication device to performreceive processing and also contains cycle information for setting thereceive window. The management information may also contain device IDinformation unique to the corresponding wireless communication device.

Other wireless communication devices receiving this managementinformation, link the management information to the device IDinformation and store it in the memory so that the correspondingwireless communication device can control the timing to perform receiveprocessing.

Therefore, according to the wireless communication device in the fourthaspect of the present invention or the wireless communication method inthe fifth aspect of the present invention, each wireless communicationdevice checks for the presence of the other devices by exchanging themanagement information, and performs asynchronous transmission based onthe receive timing described in the management information, so that awireless network can be formed. In this case, each wirelesscommunication device can communicate directly and asynchronously witheach other without installing a particular device serving as the controlstation.

Furthermore, the other wireless communication devices can sendinformation by utilizing the receive window described in the managementinformation that was received in advance. Wireless communication devicescan therefore perform asynchronous communication without being inconstant receiving standby, so that the receive function operates withlow power consumption.

Furthermore, the other wireless communication devices can performwireless communication without obtaining a means to check in advance ontransmission line usages, by transmitting information based on themanagement information received in the past, so that informationtransmission is performed in a comparatively short time.

Specifically, according to the wireless communication device in thefourth aspect of the present invention or the wireless communicationmethod in the fifth aspect of the present invention, an access controlmethod capable of avoiding conflicts during asynchronous wirelesscommunication can be obtained without using a random access controlmethod for controlling communication conflicts by carrier sensingcontrol.

Furthermore, an success control not prone to communication conflicts canbe achieved between multiple wireless communication devices, byarranging the receive window while shifting the timing so that theperiods for performing receive processing on each wireless communicationdevice do not overlap with periods of other communication devices.

Furthermore, each wireless communication device may send its ownmanagement information at each specified cycle, and managementinformation may also contain notification cycle information for sendingthe management information to other wireless communication devices.

The other wireless communication devices that received the managementinformation can furthermore check on the presence of the correspondingwireless communication device in the wireless network, and further maydecide that the wireless communication device is no longer present inthe wireless network when a specified time (for example, a notificationcycle specified in the management information) has elapsed after lastreceiving the management information.

Specifically, a wireless network system for configuring an autonomouswireless network can be achieved within the communication range of awireless communication device without having to strictly define thewireless network, by providing a function to decide there is no longer aconnection with a wireless communication device and delete it from thememory when no signals containing the identifier and timing informationare received from that wireless communication device ever a certainlength of time.

An access control method effective for use with multiple communicationdevices can also be achieved without having to install the controlstation or access point that serves as a reference in the wirelessnetwork, by installing a management information exchange area insynchronization to exchange the management information between multiplecommunication devices.

In situations when transmission with a guaranteed quality of service(QoS) is required, wireless communication with a guaranteed QoS can beeasily achieved by sending management information to notify thattransmission will be made with a guaranteed QoS as, for example, inreserved transmissions.

By sending the management information of a communication device tonotify of the presence or absence of the other communication devicescapable of communicating with that communication device, the structuralrange for a wireless network centering on that communication device canclearly be shown.

In the wireless communication device in the fourth aspect of the presentinvention or wireless communication method in the fifth aspect of thepresent invention, a wireless communication devices may receive an RTSfrom other wireless communication devices based on the receive windowdescribed in the management information, and also may return a CTS tothe transmitting source wireless communication device in response toreceiving the RTS. As a result, a connection with the correspondingwireless communication device is established to start transmittinginformation.

Accordingly, asynchronous wireless communication can be performed byRTS/CTS access control, without having to be in constant receive standbyfor detecting RTS signals.

Each wireless communication device also performs the minimum requiredreceive operation by respectively setting a minimum required receivewindow while mutually exchanging the management information. Unlike therelated art, there is therefore no need to be in constant receivestandby thereby allowing low power consumption operation. Since thereceive window need only detect if there is information addressed to itsown communication device, an extremely short receive window can be setso that operation with exceptionally low power consumption is achieved.

Furthermore, the receive operation can be simplified by setting therespective receive windows as needed, since there is no need to receiveand decode all information flowing on the transmission lines even duringsuper high speed wireless transmissions.

Information addressed to one's own communication device can be acquiredwithout having to utilize a high speed processor for receivinginformation sent in a super high speed transmission.

Here, the wireless communication device, in response to returning a CTSto the transmitting source wireless communication device, may set aninformation receive window for receiving the information from thetransmitting source wireless communication device.

After receiving the information sent from the transmitting source, thewireless communication device may send a receipt confirmation.

Furthermore, a sixth aspect of the present invention is a computerprogram written is a computer-readable format for performing wirelesscommunication processing on a computer system to send information over awireless network for asynchronous information transmission andcomprising the steps of: receiving management information from otherwireless communication devices, describing the receive processing timingof the corresponding wireless communication device; storing the receivedmanagement information while linking the received management informationto the corresponding wireless communication device; and sendinginformation by utilizing the receive processing timing described in themanagement information of the receiving destination wirelesscommunication device.

Furthermore, a seventh aspect of the present invention is a computerprogram written in a computer-readable format for performing wirelesscommunication processing on a computer system to send information over awireless network for asynchronous information transmission andcomprising the steps of: creating management information describing thereceive processing timing of one's own device; sending the managementinformation to other wireless communication devices; and receivinginformation by utilizing the receive processing timing described in themanagement information.

The computer programs of the sixth and seventh aspects of the presentinvention are defined as computer programs written in acomputer-readable format to achieve specified processing in a commutersystem. In other words, interactive effects are achieved by installingcomputer program of the sixth and seventh aspects of the presentinvention, and the same effects as in the wireless communication methodof the third and fifth aspects of the present invention can be obtained.

Further objects, characteristics and advantages of the present inventionwill become apparent from the embodiments of the present inventiondescribed while referring to the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing showing the configuration of anasynchronous wireless communication network in the first embodiment ofthe present invention;

FIG. 2 is a drawing showing an example of setting the receive timing forcommunication devices operable on a wireless network in the firstembodiment of the present invention;

FIG. 3 is a drawing showing typical management information transmittedfrom a communication device at a specific notification cycle in thefirst embodiment of the present invention;

FIG. 4 is a drawing showing a sequence example of informationtransmission between communication devices in the first embodiment ofthe present invention;

FIG. 5 is a schematic drawing showing an example of arranging receivewindows distributed to the communication devices;

FIG. 6 is a block diagram showing the functions of communication device10 operating on an asynchronous wireless network in the first embodimentof the present invention;

FIG. 7 is a time chart illustrating access control for setting amanagement information exchange area and a reserved transmission area onan asynchronous wireless network in the first embodiment of the presentinvention;

FIG. 8 is a flowchart showing the operating procedure for acommunication device capable of communicating directly andasynchronously with other communication devices on a wireless network inthat first embodiment of the present invention;

FIG. 9 is a drawing showing an example of asynchronous transmission bycommunication devices of the related art;

FIG. 10 is a schematic drawing showing the configuration of theasynchronous wireless communication network in the second embodiment ofthe present invention;

FIG. 11 is a drawing showing an example of setting widows betweencommunication devices for transmitting information on an asynchronouswireless network in the second embodiment of the present invention;

FIG. 12 is a schematic drawing showing the information transmissionsequence between communication devices on an asynchronous wirelessnetwork in the second embodiment of the present invention;

FIG. 13 is a schematic drawing showing the configuration of managementinformation P;

FIG. 14 is a schematic drawing showing the configuration of an RTS(Request to Send);

FIG. 15 is a schematic drawing showing the configuration of a CTS (Clearto Send);

FIG. 16 is a schematic drawing showing the configuration of transmissioninformation S;

FIG. 17 is a schematic drawing showing the configuration of receiptconfirmation T;

FIG. 18 is a block diagram showing the functional configuration ofcommunication device 10-2 operable on an asynchronous wireless networkin the second embodiment of the present invention;

FIG. 19 is a flowchart showing the operating procedure for acommunication device capable of communicating directly andasynchronously with other communication devices on a wireless network inthe second embodiment of the present invention; and

FIG. 20 is a flowchart showing a modified example of the operatingprocedure for a communication device for performing direct andasynchronous communication on a wireless network in the secondembodiment of the present invention.

DETAILED DESCRIPTION Best Mode For Carrying Out the Invention

The embodiments of the present invention are hereafter described indetail with reference to the drawings.

First Embodiment

The wireless network of the first embodiment of the present invention isschematically shown in FIG. 1. Each communication device within thewireless network of the present embodiment is capable of sendinginformation asynchronously. Of course synchronous informationtransmission is also applicable to the present invention.

In the example in the drawing, the communication device 1 throughcommunication device 8 are distributed spatially. The arrows in thedrawing show that each communication device can communicate with otheradjacent communication devices. A communication device 3 is capable ofdirect communication with each of communication devices 1, 4 and 6 whichare present within the communication range 13 shown by the dashed line.

A communication device 6 is capable of direct communication with each ofcommunication devices 3, 5 and 7 which are present within thecommunication range 16 shown by the dashed line.

A communication device 7 is capable of direct communication with each ofcommunication devices 5, 6 and 8 which are present within thecommunication range 17 shown by the dashed line.

The communication device may, for example, be comprised of acommunication adapter card or PC card, or computer peripheral equipmentof other configurations. The communication device may be mounted withinexternal connection equipment (not shown in drawing) such as a personalcomputer or PDA (Personal Digital Assistant) to provide wirelesstransmission capability.

Each communication device in the present embodiment can set notificationcycles for management information at specified time intervals andtransmit (or for example, broadcast) management information describinginformation on periods when receive is allowed, such as receive timinginformation showing the position to start receiving information on one'sown communication device, receive window information, and receive windowcycle information. The other communication devices that received themanagement information, however, link it with the receive number of thecorresponding communication device and store the respective receivetiming and receive windows and receive cycle.

Communication devices within the wireless network can check for thepresence of other communication devices within the network by receivingtheir management information. In other words, each communication devicecan inform other communication devices of its own presence in thewireless network by transmitting (broadcasting) management informationat specified notification cycles. Moreover, if there are communicationdevices whose notification cycle (time) elapsed (or another specifiedtime elapsed) without management information being received, then it ispossible to assume that those communication devices are no longer withinthe wireless network. Accordingly, an autonomous wireless network isformed by communication devices spatially present within the network andcapable of exchanging management information.

When communication terminals send information to each other within thistype of wireless network, the transmitting communication device findsthe receive start position of the communication device that will receivethe information, based on the receive timing, receive windows andreceive cycle described in the management information that were alreadystored, and send information on its timing. However, access control inan asynchronous wireless network of the present embodiment is mentionedin detail later on.

FIG. 2 shows an example of receive timing setting by a communicationdevice capable of operating on the wireless network of the presentembodiment.

As shown in the drawing, the cycle for repetitively sending themanagement information is set as the notification cycle. Thenotification cycle is equivalent to the time interval placed beforesending the next management information. For example, one cycle is setto as interval from several dozen milliseconds to several minutes. Asdescribed above, by sending (broadcasting) the management information ateach specified notification cycle, a communication device can notifyother communication devices within the wireless network of its ownpresence.

“receive window” is set as the time for receiving the information. Forexample, the receive window is set as the minimum required time forreturning a communication request and its confirmation. This receivewindow is set for receiving the signal in an extremely small amount oftime. The receiving section in the communication device decides ifdecoded information is present within the receive window or not. Ifdecided that information is present, then a setting can be made so thenext information is continually received even after the receive windowwas closed.

A receive window is arranged along the time axis to set the “receivetiming” used to start receive operation at a certain timing, so that theactual receive timing is designated.

A “receive cycle” or a “receive window cycle” is set for indicatingwhere the next window will be provided, and receive processing is thenperformed based on the receive cycle.

The receive window cycle can be set to any desired cycle according tothe communication device operating condition. This means that a longreceive window cycle can be set when asynchronous communication has notbeen performed over a long time, or a short receive window cycle can beset for implementing asynchronous communication without stress.

The receive window and the receive window cycle can be set to avoidconflicts between communication devices within the wireless network andin this way make efficient use of wireless transmission lines.

The example in FIG. 2 shows separate settings for each parameter;however, these may be set as fixed parameters.

FIG. 3 is an example of the management information structure for thecommunication device for sending management information at eachspecified notification cycle in the present embodiment. Informationneeded for configuring a wireless network for asynchronous communicationis described in the management information.

As shown in the figure, the management information provides fields inwhich various types of information are written, including: communicationdevice number information on an individual ID number assigned to acommunication device for transmitting that management information;notification cycle information for showing the cycle for performingmanagement information notification; receive window information forshowing the time for performing receive processing; receive timinginformation for notifying what time was set in that receive window; andreceive cycle information for designating the position where the receivewindow is periodically installed.

Besides the above basic structure, the management information maycontain other items as needed, including reserved information fornotification of reserved transmission areas; information on othercommunication devices for designating accessible communication devicesin the vicinity; an CRC (Cyclic Redundancy Check) code for identifyingif the management information is correct or not, etc.

For example, when transmission with a guaranteed communication quality(QoS: Quality of Service) is required, then the communication device canplace information for transmission with a guaranteed QoS in themanagement information and send (broadcast) it. For example, by writinga reserved transmission area setting into the reserved information fieldwithin the management information, the data transmission can then bemade to the corresponding communication device utilizing a reservedbandwidth and the QoS guaranteed.

By describing information about other accessible communication devicesinto the management information, the other devices that received themanagement information can recognize the wireless communicationenvironment of the corresponding communication device, that is, thestructure of the asynchronous wireless network configured by thecorresponding communication device that sends (broadcasts) itsmanagement information at the specified notification cycle.

These specifications describe an example of setting the managementinformation as individual parameters. However, parameters that are notneeded can be deleted as necessary. Further, if there are parametersthat must be added as management information, then these may be added asneeded.

As mentioned above, in the asynchronous wireless network of the presentembodiment, each communication device can notify other communicationdevices of its presence in the wireless network by transmitting(broadcasting) management information as shown in FIG. 3 at eachspecified notification cycle. By broadcasting the management informationin notification cycles at a rate of once in a few to once in a fewthousand times, the frequency that transmissions are sent can be keptlow and power consumption can be reduced.

To send information, the communication device for sending it must use areceive window specified in the management information of thecommunication device that will receive the information. Using thespecified receive window drastically shortens the information receiveprocessing in the communication device set with the receive window saidreceive window cycle. Use of the specified receive window also allowsthe transmitting communication device to finish sending the informationat the specified timing, and also reduces the processing load foracquiring synchronization.

By making the receive window and receive window cycle settings so thatno communication conflicts occurs among the communication devices in thewireless network, the wireless transmission lines can be efficientlyutilized.

When a communication device sends management information as shown inFIG. 3 and detects the presence or absence of other accessiblecommunication devices, then each communication device can clearly showthe range of the wireless network structure centering around itself.

FIG. 4 shows an example of the information transmission sequenceperformed by the communication device of the present embodiment. Theexample in the drawing shows the sequence for information exchange amongthe source connection device 41 serving as the source for transmittingthe asynchronous information, the transmitting source communicationdevice 42 serving as the source for transmitting the wirelesscommunication, the receiving destination communication device 43 servingas the destination for receiving that wireless communication, and thedestination connection device 44 serving as the destination forreceiving the asynchronous information.

First of all, the management information is notified (T1) to thetransmitting source communication device 42 from the receivingdestination communication device 43. The transmitting sourcecommunication device 42 can therefore detect that the receivingdestination communication device 43 is within its own communicationrange. The transmitting source communication device 42 may also notifyits management information (not shown in drawing) to the receivingdestination communication device 43 so that the receive window (notshown in drawing) or the transmitting source communication device 42 maybe set on the receiving destination communication device 43.

The time for receiving the information or, in other words, the receivewindow, is set in the receiving destination communication device 43.Information relating to the receive window such as the receive window,receive timing, and receive window cycle is also contained in themanagement information notified from the receiving destinationcommunication device 43, so the transmitting source communication device42 that received the information beforehand can know that the timingsfor receive windows W1 through W3.

Here, when the transmission information has arrived (T2) at thetransmitting source communication device 42 from the source connectiondevice 41, the transmitting source communication device 42 utilizes thetiming for the receive window W2 which is the nearest in the vicinityfrom among receive window timings on the receiving destinationcommunication device 43 and transmits the information (T3).

The receiving destination communication device 43 at this time carriesout receive operation in the period of the receive window W2, so theinformation transmission can be received.

The receive window basically is set to receive the signal in anextremely short time. However, a decision is made whether there isdecoded information in the receive window or not. When decided thatinformation is present, then the subsequent receive processing maycontinue (not shown in drawing) even after the receive window haselapsed.

When the information transmission 403 was received correctly, thereceiving destination communication device 43 conveys the receivedinformation (T4) to the destination communication device 44.

The receiving destination communication device 43 in this way receivesinformation according to a receive window and receive window cycle thatwere set beforehand. Therefore, compared to the related art which mustalways be in standby for receiving information, the receive processingtime can be drastically shortened and the power consumption reduced. Theprocessing on the transmitting source communication device 42 can alsoend just by transmitting the information the specified timing.

In the asynchronous wireless network of the present embodiment, eachcommunication device can notify other communication devices of itspresence in the wireless network by transmitting management informationcontaining receive timing information showing its own informationreceive start position, receive window information and receive cycleinformation at a specific cycle. Each communication device setsnotification periods at specified time periods to transmit managementinformation. However, when multiple communication devices set their ownrespective timings, it is preferable that the receive windows andreceive window periods be arranged so they do not mutually conflict.

FIG. 5 is a schematic drawing showing an example of arranging thereceive windows dispersed for each communication device so that thereceive window and receive window cycle do not conflict with each otherwhen multiple communication devices are present in the vicinity.

Here, the communication device 1 serving as a basis notifies othercommunication devices of its own existence within the wireless networkby transmitting management information M1. The communication device 1also established its own receive windows W11 through W14 for receivinginformation based on the receive timing and receive window cyclespecified by this management information M1.

In the present embodiment, the communication device 1 that first sendsmanagement information in the asynchronous wireless network sets themanagement information exchange area C1, so that operation proceed alongwith other communication devices present in the vicinity. Thismanagement information exchange area C1 is established at each specifiednotification cycle, and the next management information exchange area C2is established right after the management information M1 is sent thenext time. Then, management information from other communication devicesis received utilizing the period in the management information exchangearea C1 during which its own management information is not being sent.

The communication device 2 sends its own management information M2 whenthe management information M1 of the communication device 1 has beenreceived. The communication device 2 notifies other communicationdevices in the wireless network of its own presence. The communicationdevice 2 establishes receive windows W21 through W24 for receivinginformation based on the receive timing and receive window cyclesspecified by this management information M2.

In the example shown in FIG. 5, the communication device 2 sets thetiming for transmitting its own management information based on theposition of the management information exchange area C1 set by thecommunication device 1 so that no conflicts occur with the managementinformation notification timing of the communication device 1. Thecommunication device 2 then receives management information from theother communication devices by utilizing the period in the managementinformation exchange area C1 during which its own management informationis not being transmitted. The receive windows W21 through W24 are alsoestablished so no conflicts occur with the receive windows of thecommunication device 1.

Likewise, the communication device 3 sends its own managementinformation M3, notifying other communication devices in the wirelessnetwork of its own presence. The communication device 3 also establishesreceive windows W31 through W34 based on the receive timing and receivewindow cycles specified by this management information M3.

In the example shown in FIG. 5, in the communication device 3 sets thetiming for transmitting its own management information based on theposition of the management information exchange area C1 set by thecommunication device 1 so that no conflicts occur with the managementinformation notification timing of the communication device 1 andcommunication device 2. The communication device 2 then receivesmanagement information from the other communication devices by utilizingthe period in the management information exchange area C1 during whichits own measurement information is not being transmitted. The receivewindows W31 through W34 are also established so no conflicts occur withthe receive windows of the communication device 1 and communicationdevice 2.

The communication device 4 in the same way, sends its own managementinformation M4, notifying other communication devices in the wirelessnetwork of its own presence. The communication device 4 also establishesreceive windows W41 through W44 based on the receive timing and receivewindow cycles specified by this management information M4.

In the example shown in FIG. 5, the communication device 4 sets its ownmanagement information transmit timing based on the managementinformation exchange area C1 set by the communication device 1, so asnot to conflict with the management information notification timing ofthe communication device 1, communication device 2, and communicationdevice 3. The communication device 4 then receives managementinformation from the other communication devices by utilizing the periodin management information exchange area C1 during which its ownmanagement information is not being transmitted. The receive windows W41through W44 are also established so no conflicts occur with the receivewindows of the communication device 1, communication device 2 andcommunication device 3.

FIG. 6 is a block diagram showing the functions of the communicationdevice 10 in the asynchronous wireless network of the presentembodiment. As shown in the figure, the communication device 10 iscomprised of an interface 11, a memory buffer 12, a wireless transmitter13, an antenna 14, an information storage section 15, a centralprocessing unit 16, a wireless receiver 17, a time measurement section18, and an access controller 19. However, other structures may also beused to achieve the same functions as the structure in the drawing sothe invention is not limited to this structure.

The communication device 10 can also communicate asynchronously withother wireless communication devices under the overall control of thecentral processing unit 16. The central processing unit 16 is amicroprocessor and controls the equipment operation during asynchronouswireless communication by implementing operating sequence commands(program codes) stored in the information storage section 15.

The parameters required for access control in asynchronous wirelesscommunication in the present embodiment are generated in the centralprocessing unit 16, stored in the memory buffer 12 as the managementinformation and those parameters are also stored in the accesscontroller 19.

The management information is comprised of communication device numberinformation on an individual identification number assigned to thecommunication device 10; notification cycle information for reportingthe management information; receive window information for showing thetime for performing receive processing; receive timing information fornotifying what time was set in that receive window; and receive cycleinformation for designating the position where the receive window isperiodically installed (see FIG. 3).

The access controller 19 regulates the information transmitting andinformation receiving operations of the communication dewiest 10 in thewireless network based on time information from the managementinformation time and the measurement section 18. First of all, theaccess controller 19 issues instructions to the wireless transmitter 13when the transmit timing has arrived. This transmit timing referred tohere is the receive window installed in the communication device at thereceiving destination. In response to the instruction from the accesscontroller 19, the wireless transmitter 13 then sends the transmissioninformation stored in the buffer memory 12 from the antenna 14 as awireless signal, The access controller 19 issues instructions to thewireless receiver 17 when the receive timing has arrived, based on themanagement information and the time information from the timemeasurement section 18. The wireless receiver 17 then receives thewireless signal that was captured via the antenna 14.

When the wireless receiver 17 has received the management informationfrom the other communication devices in the management informationexchange area, it supplies that management information to the centralprocessing unit 16. The central processing unit 16 then appropriatelystores each parameters described in the management information, into theinformation storage section 15. This management information is thenutilized when transmitting information to that transmitting sourcecommunication device.

When the information received by the wireless receiver 17 istransmission information addressed to the wireless communication device10 itself, that information is stored in the memory buffer 12. In thememory buffer 12, that receive information is reconstructed and suppliedto the connected interface 11 (not shown in drawing). If the receivedinformation is any other information then it is discarded.

If there is any information supplied from a connected device (not shownin drawing), then the interface 11 stores that transmission informationin the memory buffer 12 and also notifies the central processor unit 16of the information on the destination for wireless transmission. Thecentral processor unit 16 then refers to other parameters received fromother communication devices in the past that are stored in theinformation storage section 15 and sends instructions to the accesscontroller 19 to process the transmission.

This series of information transmission operations starts up based oninstructions from the central processor unit 16, and the accesscontroller 19 then operates according to the timing of the timemeasurement section 18.

The central processor unit 16 then refers to the notification cycleinformation in its own management information stored in the informationstorage section 15 and instructs the access controller 19 to transmitthe management information set at the transmit timing for its ownmanagement information within the management information change area. Inresponse to this, the access controller 19 then detects the arrival ofthe transmit timing based on timing information from the timemeasurement section 18 and instructs the wireless transmitter 13 so sendthe management information at each specified notification cycle. Thewireless transmitter 13 then reads out its own management informationfrom the memory buffer 12 and transmits it via the antenna 14.

When transmitting information supplied by way of the interface 11, thecentral processor 16 temporarily stores the transmission information inthe memory buffer 12. The central processor 16 also reads out themanagement information of the receiving destination communication devicefrom the information storage section 15 in order to acquire receivewindow information, receive timing information, and receive cycleinformation (as required), and then issues an instruction for thetransmit processing to the access controller 19. In response to this,the access controller 19 detects the arrival of the transmit timingbased on timing information from the time measurement section 18 andinstructs the wireless transmitter 13 to send the information inaccordance with the receive window of the receiving destinationcommunication device. The wireless transmitter 13 then reads out thetransmission information from the memory buffer 12 and transmits it viathe antenna 14.

The central processor unit 16 then refers to the receive windowinformation, receive timing information, and receive notificationinformation in its own management information stored in the informationstorage section 15 and instructs the access controller 19 to performreceive processing. The access controller 19 detects the arrival of thereceive timing based on timing information from the time measurementsection 18 to establish the receive window at each specified receivewindow cycle and instructs the wireless receiver 17 to receive theinformation. The wireless receiver 17 then receives the information viathe antenna 14 and stores the received information in the memory buffer12. A decision is made whether there is decoded information in thereceive window or not. When decided that the information is present, thereceive processing continues even after the receive window has elapsed.

The device connected by way of the interface 11 is an informationprocessing device such as a personal computer or a PDA. This type ofinformation processing device does not basically have wirelesscommunication functions. However, by connecting a communication deviceas shown in FIG. 6, the data processed in the main unit can be sent bywireless transmission and the transmitted information from other devicescan be received.

When transmission with a guaranteed communication quality (QoS: Qualityof Service) is required, a reserved transmission area setting can bewritten into the reserved information field within the managementinformation, so that the communication device can transmit data to thecorresponding communication device by utilizing a reserved bandwidth andthe QoS guaranteed (see the previous description and FIG. 3). The timemanagement of access control in the asynchronous network of the presentembodiment is described below with reference to FIG. 7, in which themanagement information exchange area and reserved transmission area havebeen set.

The example in FIG. 7 shows the setting of the management informationexchange area after a wireless communication device has transmitted themanagement information. In that case, the communication devices in thevicinity can be notified that management information has been receivedin the management information exchange area.

When other communication devices in the vicinity detect that themanagement information exchange area has been set, the managementinformation is transmitted utilizing this management informationexchange area. Information can in this way be exchanged withcommunication devices whose management information exchange area is setand with other communication devices in that vicinity.

When the communication device 10 must transmit information at regularintervals (cycles) from its own device, then a reserved transmissionarea should be set in advance according to the quantify of data to betransmitted.

By notifying communication devices in the vicinity with managementinformation containing this reserved information, those othercommunication devices in the vicinity can be informed of periodicinformation transmission or, in other words, that reserved bandwidthtransmission will be made in the asynchronous wireless communicationnetwork.

FIG. 8 is a flowchart of the operating procedure of communication device10 capable of carrying out direct asynchronous communication with othercommunication devices in the wireless network of the present embodiment.In the actual implementation of this operating sequence, the centralprocessor 16 executes program codes stored in the information storagesection 15. The operation for direct asynchronous communication in thewireless network of the present embodiment is described in detail belowwith reference to this flowchart.

First of all, the wireless communication device 10 sets the accesscontrol parameters such as the notification cycle, receive window,receive timing, and receive cycle (step S1). These access controlparameters are stored in the information storage section 15.

Next, the wireless communication device 10 decides whether or not itsown timing has arrived (step S2). The transmit timing for the managementinformation is determined by the access control parameter settings ofstep S1. The transmit timing for the management information is setutilizing the management information exchange area so that conflicts donot mutually occur with other communication devices.

When the transmit timing for the management information has arrived, theoperation branches from “Yes” of step S2 and proceeds to step S3. Instep S3, its own device number and access control parameter areacquired, the management information configured (See FIG. 3), and thisinformation temporarily stored in the memory buffer 12. The wirelesstransmitter 13 then reads out the management information from the memorybuffer 12 and transmits (broadcasts) the management information to thewireless communication devices in the vicinity (step S4). Aftertransmitting the management information, the operation returns to stepS2. The communication device 10 in this way notifies other wirelesscommunication devices in the vicinity of its own presence in thewireless network.

On the other hand, if decided in step S2 that the transmit timing forits own management information has not arrived, then in step S5 adecision is again made on whether its own receive timing has arrived.This receive timing is determined as the receive window information,receive timing information, receive window cycle information duringsetting of the access control parameters in step S1. The transmissionlines can be efficiently utilized by setting the receive window andreceive window cycle so that communication devices within the wirelessnetwork do not conflict with each other.

When the receive timing has arrived with information addressed to itsown communication device, then the operation proceeds to step S6 fromthe “Yes” branch point of step S5 and information receive processing isperformed. Likewise, this receive processing is performed even in amanagement information exchange area that was separately set.

Next, whether or the management information of the other communicationdevices was received is decided (step S7). If decided that managementinformation of other communication devices was received then thatmanagement information is analyzed, and access control parameters of thecorresponding communication device are registered (step S8) and added ascommunication devices capable of communicating with one's own device(step S9). Here, the registration of the access control parameter isequivalent to storing the management information in the informationstorage section 15. The operation then returns to step S2.

By receiving management information from other communication devices,the communication device 10 is capable of checking their presence in theasynchronous wireless network. In other words, a wireless network isconfigured by communication devices present within a space where theirmanagement information can be mutually exchanged.

On the other hand, when decided that the management information was notreceived, the operation proceeds to step S10, and a decision furthermade if information addressed to its own communication device wasreceived. Then, information receive processing is performed only incases where the information was received, (step S11). After receiveprocessing, the operation returns to step S2.

The communication device 10 performs receive operation (See FIG. 2) inreceive windows according to the access parameter control settings ofstep S1. This receive window is set to receive signals in an extremelyshort time. A decision is made on whether decoded information is presentwithin the receive window or not. When decided that information ispresent, then the receive processing may continue to receive theinformation even after the receive window was closed.

When decided in step S5 that the receive timing has not arrived, adecision is further made in step S12 on whether there is a request forinformation transmission from an external device (for example, aninformation terminal such as a personal computer or PDA) connected byway of the interface 11.

Here, when decided that information transmission is required, the typeof transmission information is designated, and a decision made whetheror not a separate reserved transmission is required (step S13). Areserved transmission area is then set as needed (step S14) only incases where the reserved transmission is needed. The operation returnsto step S2 when no request for information transmission was received.

Next, information on the destination address for the transmissioninformation is acquired, and a decision made whether or not the accesscontrol parameters for the corresponding communication device at thedestination are already stored in the information storage section 15(step S15) In other words, a decision is made whether the managementinformation has already been received from the communication device ofthat destination address.

If the corresponding management information is already registered, thenthe operation proceeds to step S16 to acquire the access controlparameters such as the receive window information, receive timinginformation, and receive window cycle information and calculates thereceive timing at the communication device at the destination address.

Operation is in standby (step 17) until the calculated receive timing(in other words, the nearest window cycle) arrives, and the informationis then transmitted (step 18). Alter transmission, the operation returnsto step S2.

When determined in step S15 that no corresponding destinationcommunication device is registered, the operation then shifts from the“No” branch point of the applicable step to step S19. In this step thedevice connected by way of the interface 11 is notified that informationtransmission is impossible. The operation then returns to step S2.

As mentioned above, a wireless network can be configured bycommunication devices present within a space in which their managementinformation can be mutually exchanged. Though not shown in FIG. 8, aprocessing step may be executed to determine that a communication deviceis no longer present in the wireless network when its notification cyclehas elapsed (or another specified period has elapsed) after lastreceiving the management information of that communication device. Then,the management information of that communication device whose presencecan no longer be confirmed may also be deleted from the informationstorage section 15.

FIG. 9 shows an example of asynchronous wireless transmission by randomaccess control of the carrier sense method using wireless communicationdevices of the related art, for purposes of comparison with theinformation transmission operation by wireless communication devices ofthe present embodiment. In the example in this figure, asynchronoustransmission is performed by four devices comprised of communicationdevices 1 through 4.

The communication device 1 has high power consumption because receiveprocessing is constantly performed in all areas other than informationtransmit area SA1 and information transmit area SA5 that sendinformation from its own communication device to other communicationdevices. All information sent from other communication devices must bereceived and an operation to sort out information addressed to itself isrequired so a CPU with high processing capacity is needed.

The communication device 2 must also constantly perform receiveprocessing of areas other than information transmit area SA2 andinformation transmit area SA6 that send information from its owncommunication device to other communication devices. All informationsent from other communication devices muse be received, and an operationto sore out information addressed to itself is required.

The communication device 3 must also constantly perform receiveprocessing of areas other than information transmit area SA3 andinformation transmit area SA7 that send information from its owncommunication device to other communication devices. All informationsent from other communication devices must be received and an operationto sort out information addressed to itself is required.

The communication device 4 must also constantly perform receiveprocessing of areas other than information transmit area SA4 andinformation transmit area SA3 that send information from its owncommunication device to other communication devices. All informationsent from other communication devices must be received and an operationto sort out information addressed to itself is required.

Here, it should be clearly understood that unless a communication deviceascertains the presence of all other communication devices whenperforming access control such as shown in FIG. 9, there is a very highprobability that information transmission from the communication devicemay overlap with information transmission from another communicationdevice and cause a conflict.

Second Embodiment

FIG. 10 is a schematic drawing showing the configuration of theasynchronous wireless network of the second embodiment.

The example of a wireless network used in this figure has sixcommunication devices 1 through 6. More specifically, the wirelessnetwork is comprised of a communication range 13 for a communicationdevice 3. Other communication devices in the vicinity of thecommunication range of a communication device may also be present andcan automatically form a wireless network.

Other communication devices within the communication range 13 canreceive management information sent from the communication device 3 andreceive information transmitted from other communication devices. Thismanagement information is made up of receive timing informationcontaining the information receive start position for the designatedcommunication device and receive window information (described lateron). The communication device 3 can notify other communication devicesof its presence within the wireless network by transmitting(broadcasting) its own management information. Other communicationdevices can verify the presence of the communication device 3 in thewireless network by receiving the management information of thecommunication device 3.

The communication device may, for example, be comprised of a wirelessadapter card or PC card, or computer peripheral equipment of otherconfigurations. The communication device may be mounted within externalconnection equipment (not shown in drawing) such as a personal computeror PDA (Personal Digital Assistant) to provide wireless transmissioncapability.

FIG. 11 shows an example of window setting on communication devices fortransmitting information on the asynchronous wireless network of thepresent embodiment.

The communication device at the receiving destination for theinformation sets a request receive window at a timing set beforehand.This receiving destination communication device also transmits(broadcasts) in advance management information containing receive windowinformation.

On the other hand, the transmitting source communication device receivesmanagement information from the receiving destination communicationdevice, and knows the request receive window of the receivingdestination communication device ahead of time. When a request forinformation transmission is arises, this transmitting sourcecommunication device sends a communication request (RTS: Request toSend) to the receiving destination communication device by utilizing therequest receive window of the receiving destination device.

Immediately after transmitting the RTS, the transmitting sourcecommunication device sets the confirmation receive window to receive acommunication confirmation (CTS: Clear to Send) from the receivingdestination device, and then stands by.

The receiving destination communication device returns the CTS inresponse to receiving the RTS from the transmitting source communicationdevice. The receiving destination device further sets an informationreceive window for receiving information and then stands by forinformation transmission from the transmitting source communicationdevice.

The transmitting source communication device transmits information inresponse to receiving the CTS from the receiving destinationcommunication device. The receiving destination communication devicethen receives the information transmission using the previously setinformation receive window.

When an exchange of receipt confirmation is required after informationtransmission, the transmitting source communication device may set thereceipt confirmation window T_Window and a receipt confirmation T mayalso be sent back to the transmitting source communication device fromthe receiving destination communication device.

FIG. 12 is a schematic drawing showing the information transmissionsequence among the communication devices on an asynchronous network ofthe present embodiment. The example in the drawing shows the sequencefor information exchange among the source connection device 31 servingas the transmitting source for the asynchronous information to betransmitted, the transmitting source communication device 32 serving asthe source for transmitting the wireless communication, the receivingdestination communication device 33 serving as the destination forreceiving the wireless communication, and the destination connectiondevice 34 serving as the destination for conveying the asynchronousinformation.

To achieve information transmission, transmitting source communicationdevice 32 is notified beforehand of management information P of thereceiving destination communication device 33 within the wirelessnetwork. The management information (not shown in drawing) of thetransmitting source communication device 32 is notified to the receivingdestination communication device 33 in the same way.

The management information P of the receiving destination device 33contains the timing for the request receive windows Q_Window 331, 332,334 . . . set in the receiving destination device 33 itself. Thisinformation may also be specified for exchange among the communicationdevices at redundant time cycles. The transmitting source communicationdevice 32 that received the management information P may know the timingfor the request receive windows Q_Window 331, 332, 334 in advance.

The source connection device 31 for transmitting information sues as aDVD player is connected the transmitting source communication device 32via an interface. When transmission information is conveyed to thereceiving destination communication device 33 from the transmittingsource communication device 31, the timing of the nearest requestreceive window Q_Window 332 is utilized to transmit an RTS andimmediately afterward set the confirmation receive window R_Window 321for receiving the communication confirmation CTS.

If the receiving destination communication device 33 receives the RTS onthe request receive window (set by communication device 33), then a CTSis set in response to the RTS, and the information receive windowS_Window 333 is set for receiving information transmitted from thesource of the communication request.

When the transmitting source communication device 32 receives the CTS,it utilizes the information receive window S_Window 333 to transmitinformation to the receiving destination communication device 33.

When an exchange of receipt confirmation is required after informationtransmission, the transmitting source communication device 32 sets thereceipt confirmation window T_Window 322. The receipt confirmation T mayalso be sent back to the transmitting source communication device 32from the transmitting source communication device 33.

The receiving destination communication device 33 is, for example,interface-connected to a destination connection device 34 for showingtransmission information (or utilizing information in some otherformats) such as a display. The receiving destination device 33completes the information transmission sequence by outputting theinformation received from the transmitting source communication device32 to the destination connection device 34.

Further, once a connection between the communication devices 32 and 33has been secured by a sequence made up of the RTS and CTS, theninformation transmission may be continued while omitting the RTS/CTSsequence from that point.

FIG. 13 shows a configuration of management information P. Thecommunication device transmits this management information for forming awireless network, besides notifying its own receive window.

This management information is comprised of fields in which variouskinds of information are written, including: communication deviceinformation showing a device number for the applicable wirelesscommunication device; notification cycle information on managementinformation for showing the management information notification cycle;receive request window information containing parameters for receivingrequests; and communication device information on communication statusfor determining which communication devices are accessible.

The request receive window information contains information such as thetiming and cycle for setting a receive window to receive an RTS fromother communication devices. Therefore, other communication devices thatreceived that management information can know, ahead of time, the timingset on the receive window of that communication device for receiving theRTS.

Information on other accessible communication devices may also bedescribed in the management information. In this case, other devicesthat received the management information can understand the wirelesscommunication environment of the corresponding communication device,that is, the structure of the asynchronous wireless network configuredby the corresponding communication device that transmits (broadcasts)the management information set the specified notification cycle.

Besides the above basic structure, the management information may alsobe added as needed on the receiving destination communication devicewith other information or a CRC (Cyclic Redundancy Check) code fordetecting if there are errors in the management information.

When a communication device transmits (broadcasts) managementinformation according to the management information notification cyclethat was set beforehand, other communication devices can periodicallyconfirm the presence of that communication device.

Other communication devices can assume that a communication device whosenotification cycle elapsed without its management information beingreceived is probably no longer within the wireless network. This allowsforming a wireless network of communication devices spatially presentwithin an area in which their management information can be exchangedwith each other.

Of course, the communication device need not always send managementinformation periodically, and communication devices for whom a specifiedtime has elapsed since management information was last received may beeliminated one after another from the network structure.

FIG. 14 is a schematic drawing showing the structure of an RTS (Requestto Send). The transmitting source communication device can acquire theinformation receive window of the receiving destination communicationdevice by sending an RTS to the receiving destination communicationdevice.

This RTS is comprised of fields that include:

communication request transmitting source device information for showingthe source of the communication request;

communication request receiving destination device information forshowing the destination receiving the communication request;communication traffic information relating to the traffic during actualcommunication;

communication parameter information required for example incommunications such as for exchanging receipt confirmation after acommunication is completed; and a field in which a CRC code is writtenfor detecting the presence or absence of errors in communication requestinformation at the receiving destination communication device.

FIG. 13 is a schematic drawing showing the structure or a CTS (Clear toSend). When the communication device at the receiving destinationreceives an RTS (Request to Send) and accepts that request, it sendsback a CTS to the communication device at the transmitting source.

This CTS is comprised of fields in which various kinds of informationare written, including: communication confirmation transmitting sourcedevice information for showing the source of the communicationconfirmation;

communication confirmation receiving destination device information forshowing the destination receiving the communication confirmation;communication traffic information relating to the traffic during actualcommunication;

communication parameter information required for example incommunications such as for exchanging receipt confirmation after acommunication is completed; and CRC coding for detecting the presence orabsence of errors in communication confirmation information at thereceiving destination device.

FIG. 16 is a schematic drawing showing the transmission information S tobe sent by the transmitting source communication device to the receivingdestination communication device. This transmission information S ismade up of communication data information (payload) actually used in thecommunication and CRC coding for detecting transmission errors incommunication data information at the receiving destination device.

FIG. 17 is a schematic drawing showing the receipt confirmation T. Areceipt confirmation T is sent back to the transmitting sourcecommunication device when needed after receiving the transmissioninformation S is completed. This receipt confirmation T is made up ofinformation on data that was actually received and CRC coding fordetecting the presence or absence of errors in receipt confirmationinformation at the receiving destination device.

FIG. 18 is a block diagram showing the functional configuration of thecommunication device 10-2 capable of operating on the asynchronouswireless network of the present embodiment. As shown in the figure, thiscommunication device 10-2 is comprised of an interface 11, a memorybuffer 12, a wireless transmitter 13, an antenna 14, an informationstorage section 15, a central processing unit 16, a wireless receiver17, a time measurement section 18, and an access controller 19. However,other structures may also be used to achieve the same functions as thestructure in the drawing so the invention is not limited to thisstructure.

The communication device 10-2 can also communicate asynchronously withother communication devices under the overall control of the centralprocessing unit 16. The central processing unit 16 may, for example, becomprised of a microprocessor and controls the equipment operationduring asynchronous communication by executing operating sequencecommands (program codes) stored in the information storage section 15.

The parameters required for access control in asynchronous communicationin the present embodiment are generated in the central processing unit16 and stored in the memory buffer 12 as management information. Theseparameters are also stored in the access controller 19.

The management information is comprised of communication deviceinformation showing a device number assigned as an number unique to thecommunication device 10; notification cycle information on themanagement information showing the management information notificationcycle; request receive window information holding parameters forreceiving the request; communication device information for showingcommunication capability for identifying accessible communicationdevices (See FIG. 13.). Besides the above basic elements, the managementinformation may further be added with CRC cooling for detecting thepresence or absence of errors in communication confirmation informationat the receiving destination device and other information as needed.

The access controller 19 regulates the information transmission andinformation receive operation of the communication device 10 in thewireless network, based on time information from the time measurementsection 18 and management information. The access controller 19 firstsends instructions to the wireless transmitter 13 when the transmittiming has arrived. In response to the instruction from the accesscontroller 19, the wireless transmitter 13 then sends the informationstored in the buffer memory 12 from the antenna 14 as a wireless signal.

The access controller 19 also sends instructions to the wirelessreceiver 17 when the receive timing has arrived, based on timeinformation from the time measurement section 18 and managementinformation. The wireless receiver 17 then receives the wireless signalthat was via the antenna 14.

If there is any information at the interface 11 supplied from aconnected device (not shown in drawing), then the interface 11 storesthat transmission information in the memory buffer 12 and also notifiesthe central processor unit 16 of information on the transmittingdestination of that information. The central processor unit 16 thenrefers to other parameters received from other communication devices inthe past that are stored in the information storage section 15 and sendsinstructions to the access controller 19 to process the transmission.

This information transmission operation is started based on instructionsfrom the central processor unit 16, and then the access controller 19operates according to the timing of the time measurement section 18.

The central processor unit 16 then refers to the notification cycleinformation in its own management information stored in the informationstorage section 15 and instructs the access controller 19 to transmitthe management information set at the timing for transmitting its ownmanagement information within the management information exchange area.In response to that instruction, the access controller 13 then detectsthe transmit timing arrival based on time information from the timemeasurement section 18 and instructs the wireless transmitter 13 to sendthe management information at each specified notification cycle. Thewireless transmitter 13 then reads out its own management informationfrom the memory buffer 12 and transmits it via the antenna 14.

When the wireless receiver 17 has received management information in themanagement information exchange area from other communication devices,then that management information is supplied to the central processorunit 16. The central processor unit 16 then appropriately stores eachparameter described in that management information into the informationstorage section 15. The management information is utilized when sendingan RTS to the transmitting source communication device.

When transmitting information supplied by way of the interface 11, thecentral processor unit 16 temporarily stores the transmit information inthe memory storage buffer 12. The central processor unit 16 also readsout the management information of the receiving destinationcommunication device from the information storage section 15, acquiresthe request receive window information, and instructs the accesscontroller 19 to send an RTS. The access controller 19 then detects thetransmit timing arrival based on time information from the timemeasurement section 18 and instructs the wireless transmitter 13 to sendthe information synchronized with the request receive window of thecommunication device at the receiving destination. The wirelesstransmitter 13 then sends out the RTS via the antenna 14.

Immediately after the RTS is sent, the central processor unit 16 theninstructs the access controller 19 to set the confirmation receivewindow to receive the CTS from the receiving destination communicationdevice. The access controller 19 sets the communication receive window,detects the arrival of the receive timing based on time information fromthe time measurement section 18, and instructs the wireless receiver 17to perform receive processing.

When the wireless receiver 17 receives, in the confirmation receivewindow, the CTS sent from the receiving destination communicationdevice, the central processor unit 16 decodes this CTS and instructs thewireless transmitter 13 to send the transmission information. Inresponse to this instruction, the wireless transmitter 13 reads out thetransmission information from the memory buffer 12 and transmits it viathe antenna 14.

When an exchange of receipt confirmation is required after sending theinformation, the central processor unit 16 instructs the accesscontroller 19 right after the transmission ends, to set the receiptconfirmation receive window. In response to this instruction, the accesscontroller 19 sets the receipt confirmation receive window, detects thearrival of the receive timing based on time information from the timemeasurement section 18, and instructs the wireless receiver 17 toreceive the receipt confirmation.

The central processor unit 16 instructs the access controller 19 to setthe request receive window based on access control parameters that areset for the central processor 16. In response, the access controller 19detects the arrival of the receive timing based on time information fromthe time measurement section 18, and instructs the wireless receiver 17to receive the information in synchronization with its own requestreceive window.

When the wireless receiver 17 has received an RTS on the request receivewindow from another communication device, the central processor unit 16decodes this RTS and instructs the wireless transmitter 13 to send backa CTS to the transmitting source communication device. The centralprocessor unit 16 also instructs the access controller 19 to set theinformation receive window. The access controller 19 sets theinformation receive window, detects the arrival of the receive timingbased on time information from the time measurement section 18, andinstructs the wireless receiver 17 to receive the information insynchronization with the information receive window.

When the wireless receiver 17 has received transmission informationaddressed to its own wireless communication device 10, that informationis stored in the memory buffer 12. The memory buffer 12 reconstructsthat receive information and supplies it to a device connected by way ofthe interface 11 (not shown in drawing). Any other information isdiscarded if received.

When an exchange of receipt confirmation is required after sending theinformation, the central processor unit 16 instructs the wirelesstransmitter 13 to transmit the receipt confirmation after the receivingof transmission information in the information receive window from thetransmitting source communication device is finished.

The device connected by way of the interface 11 is an informationprocessing device such as a personal computer or a PDA. This type ofinformation processing device does not basically have wirelesscommunication functions. However, by connecting to the communicationdevice 10-2, the data processed in the main unit can be sent by wirelesstransmission and the transmitted information from other devices can bereceived.

FIG. 19 is a flowchart showing the operating procedure of communicationdevice 10-2 capable of carrying out direct asynchronous communicationwith other communication devices in the wireless network of the presentembodiment. In the actual implementing of this operating procedure, thecentral processor 16 executes program codes stored in the informationstorage section 15. The operation for direct asynchronous communicationin the wireless network of the present embodiment is described in detailbelow with reference to this flowchart.

When the power is turned on, the wireless communication device 10-2first sets access control parameters including the managementinformation notification cycle and request receive window information,and then sets the request receive window based on these parameters (stepS21).

Next, the wireless communication device 10-2 decides whether its ownmanagement information timing has arrived (step S22). The transmittiming for the management information is determined during setting ofthe access control parameters of step S21. The management informationtransmit timing is set utilizing the management information exchangearea so that conflicts do not mutually occur with other communicationdevices.

When the management information transmit timing has arrived, theoperation branches from “Yes” of step S22 and proceeds to step S23. Instep S23, its own device number and access control parameters areacquired, the management information configured (See FIG. 13), and thisinformation temporarily stored in the memory buffer 12. The wirelesstransmitter 13 then reads out the management information from the memorybuffer 12 and transmits (broadcasts) the management information to thewireless communication devices in the vicinity. After transmission, theprocess returns to step S22. By transmitting its own managementinformation, the communication device 10 can in this way notify otherwireless communication devices of its own presence in the wirelessnetwork.

At this time, the receiving of management information over a lengthyamount of time from another communication device can be attempted, andthe management information may be transmitted at this receive timing.

On the other hand, when decided in step S22 that the transmit timing forits own management information has not arrived, then in step S24 adecision is again made on whether there is management informationreceived from other communication devices.

When management information has been received from other communicationdevices, the process then shifts to the following step S25 from the“Yes” branch point of the decision diamond, the applicable managementinformation is stored in the information storage section 15 and theprocess then returns to step S22. The management information isafterward utilized to acquire the timing for transmitting an RTS duringinformation transmission to other applicable communication devices.

When decided in decision diamond S24 that management information was notreceived from other communication devices, the process shifts to thefollowing step S26 from the “No” branch point of the decision diamond,and a decision made whether its own request receive window has arrivedor not. when decided that the request receive window was not arrived,the process shifts to step S27 from the “No” branch point of thatdecision diamond. Here, in step S27, a decision is made whether datainformation transmitted from the device connected to the interface 11was received.

If transmitted data information was received from the device connectedto the interface 11, the process next shifts to step S28, and therequest receive window information is then acquired from the managementinformation of the receiving destination communication device stored inthe information storage section 15. A decision is then made (step S29)on whether the receive timing of the receiving destination communicationdevice has arrived.

The RTS is then sent (step S30) in response to the arrival of thereceive timing of the receiving destination communication device.Further, after sending the RTS, the confirmation receive window is set(step S31) for receiving the CTS from the receiving destinationcommunication device.

When the CTS was received on the communication confirmation window (stepS32), the information is then transmitted (step S33).

After information transmission, a decision is made (step S34) on whetheror not an exchange of receipt confirmation is required. If receiptconfirmation is required, then a decision (step S35) is further made onwhether or not there is a received receipt confirmation. When receiptconfirmation is needed, a receive window is set for receiving receiptconfirmations and the operation for receiving it from the receivingdestination communication device is performed.

When receipt confirmation is not needed or when receipt confirmation hasbeen received, the process returns to step S22 and the asynchronouswireless communication processing is sequentially repeated.

When decided in step S29 that the receive window has not arrived, or instep S32 when the CTS was not received, or in step S32 when the receiptconfirmation was not received, then the process returns to step S29 andawaits the arrival of the next receive window.

On the other hand, when the request receive window has arrived in stepS26, then the process next shifts to step S36 from the “Yes” branchpoint of that decision diamond. Operation to receive the RTS isperformed and a decision made if the RTS was received from anothercommunication device (step S37).

If the RTS was received from another communication device, a CTS istransmitted to the applicable transmitting source communication device(step 38), and also an information receive window is set for receivinginformation transmitted from the applicable transmitting sourcecommunication device (step S39) The information transmitted from thetransmitting source communication device is then received on theinformation receive window (step S40).

A decision is made (step S41) on whether receipt confirmation isnecessary after receiving the information transmission. If receiptconfirmation is required, then a decision is made (step S42) on whetherthe data was correctly accepted or not. The receipt confirmation is thentransmitted only if the data was correctly received (step S43). Theprocess then returns to step S22 and the asynchronous wirelesscommunication process is sequentially repeated.

When decided in step S37 that the RTS was not received on the requestreceive window, or when decided in step S41 that receipt confirmation isnot needed, or when decided in step S42 that data was not acceptedcorrectly, then the processes each return to step S22, and theasynchronous wireless communication process is sequentially repeated.

In the first embodiment of the present invention, the communicationdevices within the wireless network periodically establish receivewindows and utilize management information to provide notification toother communication devices. The communication device at thetransmitting source is structured to utilize the receive window of thereceiving destination communication device for all transmission ofinformation.

On the other hand, in the wireless network of the second embodiment ofthe present invention, asynchronous communication is performed by theRTS/CTS method. However, the communication device 10-2 utilizes thereceive window that it was notified by the management information onlyduring transmission of the RTS. The communication device 10-2 does notuse the receive window as specified by management information in thesending/receiving of the CTS, sending/receiving of transmissioninformation, and sending/receiving of receipt confirmation that follow.However, the communication device 10-2 does set the communicationconfirmation window, information receive window, receipt confirmationreceive window in sequence in response to transactions such assending/receiving of RTS and sending/receiving of CTS (See FIG. 11 andFIG. 12).

When performing asynchronous communication by the RTS/CTS method, avariation of the embodiment may be employed wherein only the receivewindow specified by the management information that was notified by theother communication party is utilized to perform all transmitting andreceiving operations.

FIG. 20 is a flowchart showing the operating procedure for thecommunication device 10-2 to perform asynchronous communication by theRTS/CTS method utilizing only the receive window specified by managementinformation notified to the communication device 10-2 from the othercommunication party. This operating procedure actually proceeds byexecuting program codes stored in the information storage section 15 bythe central processor unit 16. The operation of this direct asynchronouscommunication is described in detail below with reference to thisflowchart.

When the power is turned on, the wireless communication device 10-2first sets access control parameters such as the management informationnotification cycle, and request receive window information, and thensets the request receive window based on these parameters (step S51).

Next, the wireless communication device 10-2 decides whether thetransmit timing for its own management information has arrived (stepS52). The transmit timing for the management information is determinedduring setting of the access control parameters of step S51. Thetransmit timing for the management information is set utilizing themanagement information exchange area so that conflicts do not mutuallyoccur with other communication devices.

When the transmit timing for the management information has arrived, theoperation branches from “Yes” of step S52 and proceeds to step S53. Instep S53, its own device number and access control parameters areacquired, the management information configured (See FIG. 13), and thisinformation temporarily stored in the memory buffer 12. The wirelesstransmitter 13 then reads out the management information from the memorybuffer 12 and transmits (broadcasts) the management information to thewireless communication devices in the vicinity. After transmission, theprocess returns to step S52. By transmitting its own managementinformation, the communication device 10-2 can in this way notify otherwireless communication devices of its own presence in the wirelessnetwork.

At this time, the receiving of management information from anothercommunication device over a lengthy amount of time can be attempted, andthe management information may be transmitted at this receive timing.

On the other hand, when decided in step S52 that the transmit timing forits own management information has not arrived, then in step S54 adecision is again made on whether there is management informationreceived from other communication devices.

When management information has been received from other communicationdevices, the process then shifts to the following step S55 from the“Yes” branch point of the decision diamond, the applicable managementinformation is stored in the information storage section 15 and theprocess then returns to step S52. This management information isafterward utilized to acquire the timing for transmitting the RTS duringinformation transmission to other applicable communication devices.

When decided in decision diamond S54 that management information was notreceived from other communication devices, the process shifts to thefollowing step S56 from the “No” branch point of the decision diamond,and a decision made whether its own request receive window has arrivedor not. When decided that the request receive window has not arrived,the process shifts to step S57 from the “No” branch point of thatdecision diamond. Here in step S57, a decision is made whether datainformation transmitted from the device connected to the interface 11was received.

If receiving transmit data information from the device connected to theinterface 11, the process next shifts to step S58 and the requestreceive window information is then acquired from the managementinformation of the receiving destination communication device stored inthe information storage section 15. A decision is then made (step S59)on whether the receive timing of the receiving destination communicationdevice has arrived. The RTS is then sent (step S60) in response to thearrival of the receive timing of the receiving destination communicationdevice.

Next, receive operation is attempted (step S61) on the following receivewindow of the communication device 10-2 for receiving the CTS from thecommunication device on the receiving side. If the CTS could bereceived, then the information is transmitted (step S62) after awaitingarrival of the nearest receive window of the communication device on thereceiving side.

After information transmission, a decision is made (step S63) on whetheror not en exchange of receipt confirmation is required. If receiptconfirmation is required, then a decision is further made on whether ornot there is a received receipt confirmation (step S64). When receiptconfirmation is needed, a receive window is set for receiving receiptconfirmation and the receipt confirmation is received from the receivingdestination communication device.

When receipt confirmation is not needed or when receipt confirmation hasseen received, the process then returns to step S52 and the asynchronouswireless communication processing is sequentially repeated.

When decided in step S59 that the receive window has not arrived, or instep S61 when the CTS was not received, or in step S64 when the receiptconfirmation was not received, then the process returns to step S59 andawaits the arrival of the nest receive window.

On the other hand, when the request receive window has arrived in stepS56, then the process next shifts to step S56 from the “Yes” branchpoint of that decision diamond. Operation to receive the RTS isperformed and a decision made if RTS was received from anothercommunication device (step S66).

If the RTS was received from another communication device, then themanagement information of the applicable transmitting sourcecommunication device is acquired from the information storage section15, and the CTS is transmitted (step S67) after awaiting arrival of thenearest receive window. The information transmitted from thetransmitting source communication device is then received on its ownreceive window (step S68).

After receiving the transmitted information, a decision is then made(step S69) on whether receipt confirmation is necessary. It receiptconfirmation is required, then a decision is made (step S70) on whetherthe data was correctly accepted or not. And only when the data wascorrectly received, the receipt confirmation is transmitted (step S71)after awaiting arrival of the nearest receive window on the transmittingsource communication device side. The process then returns to step S52and the asynchronous wireless communication process is sequentiallyrepeatedly.

When decided in step S66 that the RTS was not received on the requestreceive window, or when decided in step S69 that receipt confirmation isnot needed, or when decided in step S70 that data was net acceptedcorrectly, then the processes each return to the appropriate step, andthe asynchronous wireless communication process is sequentiallyrepeated.

Supplemental Information

The above information described the present Invention while referring tothe designated embodiments. However, as is clear to one skilled in theart, revisions and substitutions may be made to the embodiments withoutdeparting from the scope and spirit of the present invention.

The examples in the present specifications applied the present inventionto a wireless network for performing asynchronous informationtransmission. Of course, the present invention can also be preferablyapplied to synchronous information communication networks.

In other words, the present invention was disclosed by using examplesand should not be interpreted as being limited by the contents of thepresent specifications. To determine the substance of the presentinvention; one should refer to the section containing the patent claimsin this document.

INDUSTRIAL APPLICABILITY

The present invention is capable of providing an excellent wirelesscommunication system and wireless communication control method, wirelesscommunication devices and wireless communication method an well as acomputer program, which are able to form a wireless network for directasynchronous communication while terminals mutually confirm the presenceof other terminals. In other words, the present invention is capable ofdirect asynchronous communication between wireless communication deviceswithout having to install a device that serves as the control station.

The present invention is also capable of asynchronous informationtransmission without the communication devices being in constantreceiving standby. In other words, the wireless communication devicenotifies information on its own receive timing, receive window andreceive cycle in advance, so that by receiving on that window, thecommunication devices can operate the receive function with low powerconsumption because unlike the case of the related art, there is no needto remain in constant receiving standby.

The present invention is also capable of information transmission basedon management information of other communication devices that itscommunication device received in the past. Wireless transmission can inthis way be performed without obtaining a means to check in advance onthe use of transmission lines so that information transmission isperformed in a comparatively short time.

An access control method can therefore be provided that is capable ofpreventing communication conflicts during asynchronous wirelesscommunication without, for example, having to utilize a random accesscontrol method that controls collision avoidance by carrier sensing.

Access control not prone to communication conflicts between multiplecommunication devices can also be achieved by shifting the receivetiming to be set on multiple communication devices so as to preventoverlapping.

An access control method effective for use with multiple communicationdevices can also be achieved without having to install a control stationor access point that serves as a basis in the wireless network, byinstalling a management information exchange area in synchronization toexchange management information between multiple communication devices.

Furthermore, a wireless network system for configuring an autonomouswireless network can be achieved within the communication range of awireless communication device without defining the wireless networkstrictly, by providing a function to decide there is no longer aconnection with a wireless communication device and delete it from thememory when no signals containing the identifier and timing informationare received from that wireless communication device over a certainlength of time.

Furthermore, in situations when transmission with a guaranteed qualityof service (QoS) is required, wireless communication with a guaranteedQoS can be easily achieved by communicating management information tonotify that transmission will be made with a guaranteed QoS as, forexample, in reserved transmissions.

Furthermore, by sending the management information of a communicationdevice to notify the presence or absence of the other communicationdevices capable of communicating with that communication device, thestructural area for a wireless network centering on that communicationdevice can clearly be shown.

According to the present invention, there is provided an excellentwireless communication system and wireless communication control method,a wireless communication device and wireless communication method aswell as a computer program, which are capable of asynchronous wirelesscommunication by RTS/CTS access control without the communication devicebeing in constant receiving standby for detecting RTS signals.

According to the present invention, each wireless communication deviceperforms the minimum required receive operation by respectively settinga minimum required receive window while mutually exchanging themanagement information, so that an RTS/CTS connection sequence can beachieved. Unlike the related art, there is therefore no need to be inconstant receiving standby, so operation with low power consumption isachieved. Since the receive window need only detect if there isinformation addressed to its own communication device, an extremelyshort receive window can be set so that operation with exceptionally lowpower consumption is achieved.

The receive operation can be simplified by setting the respectivereceive windows as needed, since there is no need to receive and decodeall information flowing on the transmission lines even during super highspeed wireless transmissions.

Information addressed to one's own communication device can be acquiredwithout having to utilize a high speed processor for receivinginformation sent in a super high speed transmission.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1. A wireless communication device, comprising: circuitry configured toreceive a notified management information from at least one anotherwireless communication device; detect an absence time information of atleast one accessible wireless communication device of the at least oneanother wireless communication device, based on the notified managementinformation; manage a timing of transmitting an information to the atleast one accessible wireless communication device based on the absencetime information; and transmit the information to the at least oneaccessible wireless communication device at the managed timing; whereinthe notified management information includes duration information,interval information, and start time information.